This invention relates in general to methods, systems, and apparatuses for processing signals for vehicle monitoring and specifically to methods, systems, and apparatuses for real-time processing of sensor signals for vehicle tire load monitoring.
A typical automotive vehicle may include many monitoring and control systems, for example, a cruise assist system (cruise control), an Anti-Lock Braking System (ABS), an Anti-Theft Vehicle Protection System (AVP), a Global Positioning System (GPS), and a variety of lighting, safety, climate control, and audio systems, just to name a few. These systems include many different components; including, for example, sensors, processors, transmitters, receivers, memory devices, etc. There are many varieties of each component device, for example, the sensors in an automotive vehicle may include tachometers, accelerometers, thermostats, pressure gauges, photo-electric sensors, angle sensors, yaw-rate sensors, etc.
One type of automotive vehicle system is a Tire Load Monitoring System (TLMS) disclosed in, for example, U.S. Pat. App. Pub. No. U.S. 2003/0058118 A1 published Mar. 27, 2003 in the name of Kitchener C. Wilson (herein after, “the Wilson application”), the disclosures of which are incorporated herein by reference. The Wilson application discloses an accelerometer-based TLMS that estimates tire load information based upon tire contact patch length. The tire contact patch length is calculated from the time period during which a point on the tire circumference stays in contact with the ground. In order to accomplish tire load monitoring in typical dynamic driving situations, the rate of data acquisition typically needs to be at least about 10 kHz to capture the signal from an accelerometer placed in the tire with sufficient resolution and accuracy in order to be useful in determining the tire load.
FIG. 1 is a simplified block diagram of the known real-time tire monitoring system of the Wilson application, shown generally at 30. The system 30 is incorporated in a vehicle 32 having a plurality of wheels 34 each carrying a tire 36 mounted on a rim 38. The tires 36 are shown in their loaded condition, and accordingly each has a flattened deflection contact region 40 in contact with a load-bearing surface (ground), such as a road 42.
The tire monitoring system 30 generally includes a contact region detector 50 and an associated receiver-transmitter 52 within each tire 36; a tire identifying plaque 54 attached to the sidewall of each tire; and a receiver 56, data processor 58, a distributed control subsystem 60, a data storage unit 62, an operator display 64, a remote receiver-transmitter 66 and a data bus 68 within the vehicle 32. The monitoring system 30 further includes, remote from the vehicle, a remote monitor receiver-transmitter 70 for communicating information to and from the vehicle 32; a console 72 through which a technician interacts with the vehicle 32; a magnetic wand 74 to identify the physical locations of the tires; and a tire identifying plaque scanner 76 to read the parameter information on the tire identifying plaque 54.
Generally, the contact region detector 50 functions to detect tire load-induced deflections, to time the load-induced tire deflection duration and periodicity, and to reduce signal noise. The receiver-transmitter 52 serves to receive the timing information from the contact detector 50, measure tire pressure and temperature, and transmit these data to the vehicle receiver 56. The tire identifying plaque 54 on each tire 36 carries machine-readable data relating to parameter values specific to the tire model. The in-vehicle receiver 56 is adapted to receive data transmissions from all tires 36. The data processor 58 determines tire deformation, tire load, tire molar (air) content, vehicle mass, and the distribution of vehicle mass. The distributed control system 60 includes adaptive vehicle subsystems such as brakes 60a, steering 60b, suspension 60c, engine 60d, transmission 60e, and so forth, that respond in predetermined fashions to the load, the vehicle mass and the distribution of the vehicle mass. The data storage unit 62 stores the values of parameters and of interim calculations while the operator display 64 provides status information and warnings. The remote receiver-transmitter 66 sends information to the remote monitor receiver-transmitter 70. The data bus 68 interconnects the system components.
The known approach taken to the detection of the deflection region of a loaded tire is to sense the acceleration of the rotating tire by means of an accelerometer mounted on the tire, preferably within the tire and more preferably on the inner tread lining of the tire. As the tire rotates and the accelerometer is off the flat deflection region, a high centripetal acceleration is sensed. Conversely, when the accelerometer is on the flat deflection region and not rotating, a low acceleration is sensed. The deflection points are determined at the points where the acceleration transitions between the high and low values.